Stimulation of the stomach in response to sensed parameters to treat obesity

ABSTRACT

A neurostimulation kit and a method of treating a patient are provided. The kit comprises a stimulation backing that includes a flat, electrically insulative, body having a pair of opposing first and second planar surfaces, and an electrode affixed to the first surface of the insulative body. The stimulation backing is implanted within a patient and affixed therein to place the electrode into contact with a tissue surface. The kit comprises a neurostimulator including a housing and stimulation circuitry contained within the housing. The neurostimulator is implanted within the patient by affixing the housing to the second surface of the insulative body, such that the stimulation circuitry is electrically coupled to the electrode.

RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 11/295,783, filed Dec. 6, 2005, which claims the priority under35 U.S.C. § 119(e) of previous U.S. Provisional Patent Application No.60/633,830, filed Dec. 6, 2004. The entire disclosures of the aboveapplications are expressly incorporated herein by reference.

BACKGROUND

Obesity is one of the most prevalent public heath problems in the UnitedStates and affects millions of Americans. An especially severe type ofobesity, called morbid obesity, is characterized by a body mass indexgreater than or equal to 40 or a body weight that is 100 pounds overnormal weight.

Recent studies have shown that over 300,000 deaths are caused by obesityin the United States each year. In addition, millions suffer brokenbones, social isolation, arthritis, sleep apnea, asphyxiation, heartattacks, diabetes, and other medical conditions that are caused orexacerbated by obesity.

Patients suffering from obesity have very limited treatment options. Forexample, drugs such as sibutramine, diethylproprion, mazindol,phentermine, phenylpropanolamine, and orlistat are often used to treatobesity. However, these drugs are effective only for short-term use andhave many adverse side-effects.

Another treatment option for obesity is surgery. For example, aprocedure known as “stomach stapling” reduces the effective size of thestomach and the length of the nutrient-absorbing small intestine totreat obesity. However, surgery is highly invasive and is oftenassociated with both acute and chronic complications including, but notlimited to, infection, digestive problems, and deficiency in essentialnutrients.

SUMMARY

In accordance with a first aspect of the present inventions, aneurostimulation kit comprises a stimulation backing that includes aflat, electrically insulative, body having a pair of opposing first andsecond planar surfaces, and an electrode affixed to the first surface ofthe insulative body. The stimulation backing is configured for beingimplanted within a patient and affixed therein to place the electrodeinto contact with a tissue surface of the patient. In one embodiment,the insulative body is flexible to conform to the curvature of thetissue surface. The insulative body may be composed of an electricallyinsulative material selected from the group consisting of silicone,ceramic, glass, and polyurethane. In an optional embodiment, thestimulation backing includes a plurality of suture holes formed withinthe insulative body and/or a hooks or barbs located on the first surfaceof the insulative body.

The neurostimulation kit comprises a neurostimulator including a housingand stimulation circuitry contained within the housing. Theneurostimulator may include a power source contained within the housing.The neurostimulator may be a microstimulator, e.g., the housing may havean internal space equal to or less than three cubic centimeters. Theneurostimulator is configured for being implanted within the patient byaffixing the housing to the second surface of the insulative body, suchthat the stimulation circuitry is electrically coupled to the electrode.In one embodiment, the stimulation backing includes an electricallyconductive via coupled to the electrode, and the stimulation circuitryof the neurostimulator is electrically coupled to the via when thehousing is affixed to the second surface of the insulative body. Inanother embodiment, the neurostimulator includes a power sourcecontained within the housing.

In accordance with a second aspect of the present inventions, a methodof treating a patient using the neurostimulation kit comprises affixingthe insulative body within the patient, thereby placing the electrodeinto contact with a tissue surface of the patient. In one method, theinsulative body is conformed to the curvature of the tissue surface. Inanother method, the housing is affixed to the second surface of theinsulative body after the insulative body has been affixed within thepatient. The method further comprises affixing the housing to the secondsurface of the insulative body, such that the stimulation circuitry iselectrically coupled to the electrode. In one method, the insulativebody is sutured to the tissue surface or affixed to the tissue surfacevia hooks or barbs.

The method further comprises operating the neurostimulator to conveystimulation energy from the stimulation circuitry to the tissue surfacevia the electrode to treat the patient. In one method, the stimulationbacking includes an electrically conductive via coupled to theelectrode, in which case, the stimulation circuitry of theneurostimulator is electrically coupled to the via when the housing isaffixed to the second surface of the insulative body. In another method,the insulative body is affixed to a stomach of the patient, therebyplacing the electrode into contact with an external surface of thepatient. If the patient suffers from obesity, the stimulation energy maybe conveyed from the stimulation circuitry to the external surface ofthe stomach treats the obesity

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings illustrate various embodiments of the presentinvention and are a part of the specification. The illustratedembodiments are merely examples of the present invention and do notlimit the scope of the invention.

FIG. 1A is an exemplary diagram of the stomach.

FIG. 1B shows various branches of the anterior vagal trunk thatinnervate the stomach.

FIG. 1C shows various branches of the posterior vagal trunk thatinnervate the stomach.

FIG. 2 illustrates an exemplary stimulator that may be used to apply astimulus to the stomach according to principles described herein.

FIG. 3 illustrates an exemplary microstimulator that may be used as thestimulator according to principles described herein.

FIG. 4 depicts a number of stimulators configured to communicate witheach other and/or with one or more external devices according toprinciples described herein.

FIG. 5 illustrates an exemplary implanted stimulator that is coupled tothe stomach according to principles described herein.

FIG. 6A is a perspective view of an exemplary insulative backing thatmay be used to couple the stimulator directly to the stomach accordingto principles described herein.

FIG. 6B is a perspective view of an exemplary insulative backing havinga number of hooks configured to secure the backing to the stomachaccording to principles described herein.

FIG. 6C is a top view of the insulative backing illustrated in FIG. 6Aaccording to principles described herein.

FIGS. 7A-7H illustrate a number of exemplary electrode contactarrangements that may be disposed on the first surface of the insulativebacking according to principles described herein.

FIG. 8 is a cross-sectional side view of an insulative backing andstimulator coupled to the stomach according to principles describedherein.

FIG. 9 illustrates an exemplary configuration wherein multiplestimulators are coupled to the stomach according to principles describedherein.

FIG. 10 illustrates an exemplary configuration wherein a stimulator isconfigured to stimulate the stomach via a number of electrodes disposedon a lead according to principles described herein.

Throughout the drawings, identical reference numbers designate similar,but not necessarily identical, elements.

DETAILED DESCRIPTION

Systems and methods for treating an obese patient are described herein.One or more sensors are configured to sense one or more physicalparameters of the patient. The physical parameters may include, but arenot limited to, stomach distension, stomach strain, an electrical signalproduced by the stomach, a rate of digestion of food within the stomach,food intake into the stomach, one or more gastric slow waves produced bythe stomach, or any other obesity factor. One or more implantedstimulators are configured to apply a stimulus to the stomach inresponse to the sensed parameters.

In the following description, for purposes of explanation, numerousspecific details are set forth in order to provide a thoroughunderstanding of the present systems and methods. It will be apparent,however, to one skilled in the art that the present systems and methodsmay be practiced without these specific details. Reference in thespecification to “one embodiment” or “an embodiment” means that aparticular feature, structure, or characteristic described in connectionwith the embodiment is included in at least one embodiment. Theappearance of the phrase “in one embodiment” in various places in thespecification are not necessarily all referring to the same embodiment.

FIG. 1A is an exemplary diagram of a stomach (10). As shown in FIG. 1A,the shape of the stomach (10) as viewed from the side has two curves,the lesser curvature (25) and the greater curvature (26), whichrespectively follow the upper and lower surfaces of the stomach (10).The cardia or proximal stomach (20) is located in the upper left portionof the stomach (10) and serves as the junction between the esophagus(12) and the body (22) of the stomach (10). The fundus (21), which isalso located in the upper portion of the stomach (10), produces acid andpepsin that help digest food. The lower portion of the stomach (10) isknown as the distal stomach and includes the antrum (23) and pylorus(24). The antrum (23) is where food is mixed with gastric juice. Thepylorus (24) acts as a valve to control emptying of the stomach contentsinto the small intestine (11).

The stomach (10) has five nested layers of tissue. The innermost layeris where stomach acid and digestive enzymes are made and is called themucosa. A supporting layer, know as the submucosa, surrounds the mucosa.The mucosa and submucosa are surrounded by a layer of muscle, known asthe muscularis, that moves and mixes the stomach contents. The next twolayers, the subserosa and the outermost serosa, act as wrapping layersfor the stomach (10).

Innervation of the stomach (10) is provided directly by the vagi nervesand through subsidiary plexuses of the celiac plexus. FIG. 1B showsvarious branches of the anterior vagal trunk (13), which is derived fromthe left vagus nerve. The hepatic branch (14) runs through the upperpart of the lesser omentum and joins the plexus on the hepatic arteryand portal vein. The celiac branch (15) follows the left gastric arteryto the celiac plexus. The gastric branch (16), the largest of the three,follows the lesser curvature (25) of the stomach (10) and distributesanterior gastric branches to the distal portions of the stomach (10),i.e., those portions of the stomach (10) adjacent the entrance to thesmall intestine (11).

FIG. 1C shows various branches of the posterior vagal trunk (17), whichinnervates the posterior surface of the stomach (10). The posteriorvagal trunk (17) is derived largely, but not entirely from the rightvagus nerve.

Both sympathetic efferent and afferent nerves to the stomach (10) arederived from T6-T9 spinal cord segments. These nerve fibers aretransmitted by the greater thoracic splanchnic nerve. Preganglionicfibers relay in the celiac ganglia and the nerves reach the stomach (10)along the branches of the celiac artery.

As used herein and in the appended claims, the term “food” will be usedto refer generally to any type of nutrient bearing substance in whateverform, e.g., food and/or drink, that enters the stomach (10). Food thatis input into the stomach (10) enters through the esophagus (12), passesthrough the stomach (10) and exits at the distal end of the stomach (10)into the small intestine (11). A typical stomach (10) generateselectrical pulses which signal to the neurological system of a personthat the stomach is full and that the person should stop eating.

The stomach (10) is emptied as a result of coordinated gastriccontractions (motility). Without these coordinated contractions,digestion and absorption of dietary nutrients cannot take place. Thus,impairment of gastric contractions may result in delayed emptying of thestomach (10).

Gastric contractions are regulated by myoelectrical activity of thestomach (10), called slow waves. Gastric slow waves originate in theproximal portion of the stomach (10), e.g., near the esophagus (12), andpropagate distally toward the small intestine (11). Gastric slow wavesdetermine the maximum frequency, propagation velocity, and propagationdirection of gastric contractions. The normal frequency of the gastricslow waves is about three cycles per minute (cpm) in humans.Abnormalities in gastric slow waves lead to gastric motor disorders andhave been frequently observed in patients with functional disorders ofthe stomach, such as gastroparesis, functional dyspepsia, anorexia, etc.Some studies have shown that patients with obesity have an abnormallyrapid rate of gastric slow waves.

As will be explained in more detail below, an obese patient may betreated by applying a stimulus to the stomach. In some examples, thestimulus may cause the patient to feel a sensation of fullness whichhelps the patient limit food intake. A stimulus may also be applied toslow an abnormally rapid rate of gastric slow waves causing the stomachof an obese patient to process food at a more normal rate and again helpthe patient limit food intake. The stimulus may be applied to anyportion of the stomach as best suits a particular patient or particularcondition. For example, the stimulus may be applied to one or more wallsof the stomach, one or more nerves that innervate the stomach, one ormore blood vessels that supply the stomach, or any other tissue withinthe stomach. Consequently, a stimulator may be implanted in a patient todeliver a stimulus to the stomach to treat obesity. The presentspecification will describe methods and systems for implanting such astimulator to most conveniently treat obesity.

As used herein, and in the appended claims, the term “stimulator” willbe used broadly to refer to any device that delivers a stimulus, such asan electrical stimulation current, one or more drugs or other chemicalstimulation, thermal stimulation, electromagnetic stimulation,mechanical stimulation, and/or any other suitable stimulation to thestomach. Thus, the term “stimulator” includes, but is not limited to, astimulator, microstimulator, implantable pulse generator (IPG), systemcontrol unit, or similar device. As used herein and the appended claims,any reference to stimulating the stomach will encompass stimulating anyselected portion of the stomach, including, but not limited to a wall ofthe stomach, a nerve that innervate the stomach, a blood vessel thatsupplies the stomach, or any other tissue within the stomach.

To facilitate an understanding of the methods of stimulating the stomachwith an implanted stimulator, a more detailed description of thestimulator and its operation will now be given with reference to thefigures. FIG. 2 illustrates an exemplary stimulator (140) that may beimplanted within a patient (150) and used to apply a stimulus to thestomach, e.g., an electrical stimulation of the stomach, an infusion ofone or more drugs at the stomach, or both. The electrical stimulationfunction of the stimulator (140) will be described first, followed by anexplanation of the possible drug delivery function of the stimulator(140). It will be understood, however, that the stimulator (140) may beconfigured to provide only electrical stimulation, only a drugstimulation, both types of stimulation, or any other type of stimulationas best suits a particular patient.

The exemplary stimulator (140) shown in FIG. 2 is configured to provideelectrical stimulation to the stomach and may include a lead (141)having a proximal end coupled to the body of the stimulator (140). Thelead (141) also includes a number of electrodes (142) configured toapply an electrical stimulation current to the stomach. The lead (141)may include any number of electrodes (142) as best serves a particularapplication. The electrodes (142) may be arranged as an array, forexample, having at least two or at least four collinear electrodes. Insome embodiments, the electrodes (142) are alternatively inductivelycoupled to the stimulator (140). The lead (141) may be thin (e.g., lessthan 3 millimeters in diameter) such that the lead (141) may bepositioned near the stomach. In some alternative examples, as will beillustrated in connection with FIG. 3, the stimulator (140) is leadless.

As illustrated in FIG. 2, the stimulator (140) includes a number ofcomponents. It will be recognized that the stimulator (140) may includeadditional and/or alternative components as best serves a particularapplication. A power source (145) is configured to output voltage usedto supply the various components within the stimulator (140) with powerand/or to generate the power used for electrical stimulation. The powersource (145) may be a primary battery, a rechargeable battery, a supercapacitor, a nuclear battery, a mechanical resonator, an infraredcollector (receiving, e.g., infrared energy through the skin), athermally-powered energy source (where, e.g., memory-shaped alloysexposed to a minimal temperature difference generate power), a flexuralpowered energy source (where a flexible section subject to flexuralforces is part of the stimulator), a bioenergy power source (where achemical reaction provides an energy source), a fuel cell, abioelectrical cell (where two or more electrodes use tissue-generatedpotentials and currents to capture energy and convert it to useablepower), an osmotic pressure pump (where mechanical energy is generateddue to fluid ingress), or the like. Alternatively, the stimulator (140)may include one or more components configured to receive power fromanother medical device that is implanted within the patient.

When the power source (145) is a battery, it may be a lithium-ionbattery or other suitable type of battery. When the power source (145)is a rechargeable battery, it may be recharged from an external systemthrough a power link such as a radio frequency (RF) power link. One typeof rechargeable battery that may be used is described in InternationalPublication WO 01/82398 A1, published Nov. 1, 2001, and/or WO 03/005465A1, published Jan. 16, 2003, both of which are incorporated herein byreference in their respective entireties. Other battery constructiontechniques that may be used to make a power source (145) include thoseshown, e.g., in U.S. Pat. Nos. 6,280,873; 6,458,171, and U.S.Publications 2001/0046625 A1 and 2001/0053476 A1, all of which areincorporated herein by reference in their respective entireties.Recharging can be performed using an external charger.

The stimulator (140) may also include a coil (148) configured to receiveand/or emit a magnetic field (also referred to as a radio frequency (RF)field) that is used to communicate with, or receive power from, one ormore external devices (151, 153, 155). Such communication and/or powertransfer may include, but is not limited to, transcutaneously receivingdata from the external device, transmitting data to the external device,and/or receiving power used to recharge the power source (145).

For example, an external battery charging system (EBCS) (151) mayprovide power used to recharge the power source (145) via an RF link(152). External devices including, but not limited to, a hand heldprogrammer (HHP) (155), clinician programming system (CPS) (157), and/ora manufacturing and diagnostic system (MDS) (153) may be configured toactivate, deactivate, program, and test the stimulator (140) via one ormore RF links (154, 156). It will be recognized that the links, whichare RF links (152, 154, 156) in the illustrated example, may be any typeof link used to transmit data or energy, such as an optical link, athermal link, or any other energy-coupling link. One or more of theseexternal devices (153, 155, 157) may also be used to control theinfusion of one or more drugs at the stomach to treat obesity.

Additionally, if multiple external devices are used in the treatment ofa patient, there may be some communication among those external devices,as well as with the implanted stimulator (140). Again, any type of linkfor transmitting data or energy may be used among the various devicesillustrated. For example, the CPS (157) may communicate with the HHP(155) via an infrared (IR) link (158), with the MDS (153) via an IR link(161), and/or directly with the stimulator (140) via an RF link (160).As indicated, these communication links (158, 161, 160) are notnecessarily limited to IR and RF links and may include any other type ofcommunication link. Likewise, the MDS (153) may communicate with the HHP(155) via an IR link (159) or via any other suitable communication link.

The HHP (155), MDS (153), CPS (157), and EBCS (151) are merelyillustrative of the many different external devices that may be used inconnection with the stimulator (140). Furthermore, it will be recognizedthat the functions performed by any two or more of the HHP (155), MDS(153), CPS (157), and EBCS (151) may be performed by a single externaldevice. One or more of the external devices (153, 155, 157) may beembedded in a seat cushion, mattress cover, pillow, garment, belt,strap, pouch, or the like so as to be positioned near the implantedstimulator (140) when in use.

The stimulator (140) may also include electrical circuitry (144)configured to produce electrical stimulation pulses that are deliveredto the stomach via the electrodes (142). In some embodiments, thestimulator (140) may be configured to produce monopolar stimulation. Thestimulator (140) may alternatively or additionally be configured toproduce multipolar stimulation including, but not limited to, bipolar ortripolar stimulation.

The electrical circuitry (144) may include one or more processorsconfigured to decode stimulation parameters and generate the stimulationpulses. In some embodiments, the stimulator (140) has at least fourchannels and drives up to sixteen electrodes or more. The electricalcircuitry (144) may include additional circuitry such as capacitors,integrated circuits, resistors, coils, and the like configured toperform a variety of functions as best serves a particular application.

The stimulator (140) may also include a programmable memory unit (146)for storing one or more sets of data and/or stimulation parameters. Thestimulation parameters may include, but are not limited to, electricalstimulation parameters, drug stimulation parameters, and other types ofstimulation parameters. The programmable memory (146) allows a patient,clinician, or other user of the stimulator (140) to adjust thestimulation parameters such that the stimulation applied by thestimulator (140) is safe and efficacious for treatment of a particularpatient. The different types of stimulation parameters (e.g., electricalstimulation parameters and drug stimulation parameters) may becontrolled independently. However, in some instances, the differenttypes of stimulation parameters are coupled. For example, electricalstimulation may be programmed to occur only during drug stimulation orvice versa. Alternatively, the different types of stimulation may beapplied at different times or with only some overlap. The programmablememory (146) may be any type of memory unit such as, but not limited to,random access memory (RAM), static RAM (SRAM), a hard drive, or thelike.

The electrical stimulation parameters may control various parameters ofthe stimulation current applied to the stomach including, but notlimited to, the frequency, pulse width, amplitude, electrode polarityconfiguration (i.e., anode-cathode assignment), burst pattern (e.g.,burst on time and burst off time), duty cycle or burst repeat interval,ramp on time, and ramp off time of the stimulation current that isapplied to the stomach. The drug stimulation parameters may controlvarious parameters including, but not limited to, the amount of drugsinfused at the stomach, the rate of drug infusion, and the frequency ofdrug infusion. For example, the drug stimulation parameters may causethe drug infusion rate to be intermittent, constant, or bolus. Otherstimulation parameters that characterize other classes of stimuli arepossible. For example, when tissue is stimulated using electromagneticradiation, the stimulation parameters may characterize the intensity,wavelength, and timing of the electromagnetic radiation stimuli. Whentissue is stimulated using mechanical stimuli, the stimulationparameters may characterize the pressure, displacement, frequency, andtiming of the mechanical stimuli.

Specific stimulation parameters may have different effects on differentpatients and/or types of obesity. Thus, in some embodiments, thestimulation parameters may be adjusted by the patient, a clinician, orother user of the stimulator (140) as best serves a particular patient.The stimulation parameters may also be automatically adjusted by thestimulator (140), as will be described below. For example, the amplitudeof the stimulus current applied to a nerve that innervates the stomachmay be adjusted to have a relatively low value so as to targetrelatively large diameter fibers of the nerve. The stimulator (140) mayalso increase excitement of nerves in the stomach by applying astimulation current having a relatively low frequency (e.g., less than100 Hz) to the stomach. The stimulator (140) may also decreaseexcitement of nerves in the stomach by applying a relatively highfrequency (e.g., greater than 100 Hz) to the stomach. The stimulator(140) may also be programmed to apply the stimulation current to thestomach intermittently or continuously. Different stimuli may be appliedto determine which will help a particular patient feel a sensation offullness or help the patient's stomach process food at a normal rate soas to help the patient limit the intake of unnecessary caloriescontributing to the obesity.

Additionally, the exemplary stimulator (140) shown in FIG. 2 isconfigured to provide drug stimulation to a patient by applying one ormore drugs to the stomach. For this purpose, a pump (147) may also beincluded within the stimulator (140). The pump (147) is configured tostore and dispense one or more drugs, for example, through a catheter(143). The catheter (143) is coupled at a proximal end to the stimulator(140) and may have an infusion outlet (149) for infusing dosages of theone or more drugs at the stomach. In some embodiments, the stimulator(140) may include multiple catheters (143) and/or pumps (147) forstoring and infusing dosages of the one or more drugs at the stomach.

The pump (147) or controlled drug release device described herein mayinclude any of a variety of different drug delivery systems. Controlleddrug release devices based upon a mechanical or electromechanicalinfusion pump may be used. In other examples, the controlled drugrelease device can include a diffusion-based delivery system, e.g.,erosion-based delivery systems (e.g., polymer-impregnated with drugplaced within a drug-impermeable reservoir in communication with thedrug delivery conduit of a catheter), electrodiffusion systems, and thelike. Another example is a convective drug delivery system, e.g.,systems based upon electroosmosis, vapor pressure pumps, electrolyticpumps, effervescent pumps, piezoelectric pumps and osmotic pumps.Another example is a micro-drug pump.

Exemplary pumps (147) or controlled drug release devices suitable foruse as described herein include, but are not necessarily limited to,those disclosed in U.S. Pat. Nos. 3,760,984; 3,845,770; 3,916,899;3,923,426; 3,987,790; 3,995,631; 3,916,899; 4,016,880; 4,036,228;4,111,202; 4,111,203; 4,203,440; 4,203,442; 4,210,139; 4,327,725;4,360,019; 4,487,603; 4,627,850; 4,692,147; 4,725,852; 4,865,845;5,057,318; 5,059,423; 5,112,614; 5,137,727; 5,234,692; 5,234,693;5,728,396; 6,368,315 and the like. Additional exemplary drug pumpssuitable for use as described herein include, but are not necessarilylimited to, those disclosed in U.S. Pat. Nos. 4,562,751; 4,678,408;4,685,903; 5,080,653; 5,097,122; 6,740,072; and 6,770,067. Exemplarymicro-drug pumps suitable for use as described herein include, but arenot necessarily limited to, those disclosed in U.S. Pat. Nos. 5,234,692;5,234,693; 5,728,396; 6,368,315; 6,666,845; and 6,620,151. All of theselisted patents are incorporated herein by reference in their respectiveentireties.

The one or more drugs applied by the stimulator (140) may include anydrug or other substance configured to treat obesity. For example, thedrugs may include, but are not limited to, peptides, cholecystokinin(CCK), peptide YY (PYY), Urocortin, corticotrophin-releasing factors(CRF), sibutramine, diethylproprion, mazindol, phentermine,phenylpropanolamine, and orlistat. The one or more drugs mayadditionally or alternatively include, but are not limited to,medications, anesthetic agents, synthetic or natural peptides orhormones, neurotransmitters, cytokines, and other intracellular andintercellular chemicals.

The one or more drugs may also include excitatory neurotransmitteragonists (e.g., norepinephrine, epinephrine, glutamate, acetylcholine,serotonin, dopamine), agonists thereof, and agents that act to increaselevels of an excitatory neurotransmitter(s) (e.g., edrophonium;Mestinon; trazodone; SSRIs (e.g., flouxetine, paroxetine, sertraline,citalopram and fluvoxamine); tricyclic antidepressants (e.g.,imipramine, amitriptyline, doxepin, desipramine, trimipramine andnortriptyline), monoamine oxidase inhibitors (e.g., phenelzine,tranylcypromine, isocarboxasid)). The one or more drugs may also includeinhibitory neurotransmitters (e.g., dopamine, glycine, andgamma-aminobutyric acid (GABA)), agonists thereof, and agents that actto increase levels of an inhibitory neurotransmitter(s) (e.g.,benzodiasepine (e.g., chlordiazepoxide, clonazepam, diazepam, lorazepam,oxazepam, prazepam alprazolam); flurazepam, temazepam, or triazolam).

The stimulator (140) may also include a sensor device (203) configuredto sense any of a number of indicators related to stomach activity,digestion, or any other factor related to obesity. For example, thesensor (203) may include a pressure sensor or transducer, a straingauge, a force transducer, or some other device configured to sensestomach distension that occurs as a result of food intake. In someexamples, the sensor (203) may be located on the lead (141). The sensor(203) may alternatively be a separate device configured to communicatewith the stimulator (140). The sensor (203) will be described in moredetail below.

The stimulator (140) of FIG. 2 is illustrative of many types ofstimulators that may be used to stimulate the stomach to treat obesity.For example, the stimulator (140) may include an implantable pulsegenerator (IPG) coupled to one or more leads having a number ofelectrodes, a spinal cord stimulator (SCS), a drug pump (mentionedpreviously), a micro-drug pump (mentioned previously), or any other typeof implantable stimulator configured to deliver a stimulus to thestomach. Exemplary IPGs suitable for use as described herein include,but are not limited to, those disclosed in U.S. Pat. Nos. 6,381,496,6,553,263; and 6,760,626. Exemplary spinal cord stimulators suitable foruse as described herein include, but are not limited to, those disclosedin U.S. Pat. Nos. 5,501,703; 6,487,446; and 6,516,227. All of theselisted patents are incorporated herein by reference in their respectiveentireties.

Alternatively, the stimulator (140) may include an implantablemicrostimulator, such as a BION® microstimulator (Advanced Bionics®Corporation, Valencia, Calif.). Various details associated with themanufacture, operation, and use of implantable microstimulators aredisclosed in U.S. Pat. Nos. 5,193,539; 5,193,540; 5,312,439; 6,185,452;6,164,284; 6,208,894; and 6,051,017 and U.S. patent application entitled“Affixation Member for Implantable Stimulators” to Whitehurst, et al.,client docket number AB-525U, filed Nov. 23, 2005. All of these listedpatents and application are incorporated herein by reference in theirrespective entireties.

FIG. 3 illustrates an exemplary microstimulator (200) that may be usedas the stimulator (140; FIG. 2) described herein. Other configurationsof the microstimulator (200) are possible, as shown in theabove-referenced patents and as described further below.

As shown in FIG. 3, the microstimulator (200) may include the powersource (145), programmable memory (146), electrical circuitry (144),sensor (203), and pump (147) described in connection with FIG. 2. Thesecomponents are housed within a capsule or housing (202). The capsule(202) may be a thin, elongated cylinder or any other shape as bestserves a particular application. The shape of the capsule (202) may bedetermined by the structure of the desired target nerve, the surroundingarea, and the method of implantation. In some embodiments, the capsule(202) is substantially equal to or less than three cubic centimeters.

In some embodiments, the microstimulator (200) may include two or moreleadless electrodes (142). Either or both of the electrodes (142) mayalternatively be located at the ends of short, flexible leads asdescribed in U.S. patent application Ser. No. 09/624,130, filed Jul. 24,2000, which is incorporated herein by reference in its entirety. The useof such leads permits, among other things, electrical stimulation to bedirected more locally to targeted tissue(s) a short distance from thesurgical fixation of the bulk of the microstimulator (200), whileallowing most elements of the microstimulator (200) to be located in amore surgically convenient site. This minimizes the distance traversedand the surgical planes crossed by the microstimulator (200) and anylead(s).

The external surfaces of the microstimulator (200) may advantageously becomposed of biocompatible materials. For example, the capsule (202) maybe made of glass, ceramic, metal, or any other material that provides ahermetic package that will exclude water vapor but permit passage ofelectromagnetic fields used to transmit data and/or power. Theelectrodes (142) may be made of a noble or refractory metal or compound,such as platinum, iridium, tantalum, titanium, titanium nitride, niobiumor alloys of any of these, in order to avoid corrosion or electrolysiswhich could damage the surrounding tissues and the device.

The microstimulator (200) may also include one or more infusion outlets(201). The infusion outlets (201) facilitate the infusion of one or moredrugs at the stomach to treat obesity. The infusion outlets (201) maydispense one or more drugs directly to the treatment site.Alternatively, as will be described in more detail below, catheters maybe coupled to the infusion outlets (201) to deliver the drug therapy toa treatment site some distance from the body of the microstimulator(200). The stimulator (200) of FIG. 3 also includes electrodes (142-1and 142-2) at either end of the capsule (202). One of the electrodes(142) may be designated as a stimulating electrode to be placed close tothe treatment site and one of the electrodes (142) may be designated asan indifferent electrode used to complete a stimulation circuit.

The microstimulator (200) may be implanted within a patient with asurgical tool such as a hypodermic needle, bore needle, or any othertool specially designed for the purpose. Alternatively, themicrostimulator (200) may be implanted using endoscopic or laparoscopictechniques.

A stimulator may be configured to operate independently. Alternatively,as shown in FIG. 4 and described in more detail below, the stimulator(140) may be configured to operate in a coordinated manner with one ormore additional stimulators, other implanted devices, or other devicesexternal to the patient's body. For instance, a first stimulator maycontrol or operate under the control of a second stimulator, otherimplanted device, or other device external to the patient's body. Thestimulator (140) may be configured to communicate with other implantedstimulators, other implanted devices, or other devices external to thepatient's body via an RF link, an untrasonic link, an optical link, orany other type of communication link. For example, the stimulator (140)may be configured to communicate with an external remote control unitthat is capable of sending commands and/or data to the stimulator (140)and that is configured to receive commands and/or data from thestimulator (140).

In order to determine the strength and/or duration of electricalstimulation and/or amount and/or type(s) of stimulating drug(s) requiredto most effectively treat obesity, various indicators of stomachactivity, obesity, and/or a patient's response to treatment may besensed or measured. These indicators include, but are not limited to,pressure against the stomach wall, stomach distension, stomach strain,naturally occurring electrical activity within the stomach (e.g.,gastric slow waves), a rate of digestion of food within the stomach,and/or any other activity within the stomach. The indicators mayadditionally or alternatively include electrical activity of the brain(e.g., EEG); neurotransmitter levels; hormone levels; metabolic activityin the brain; blood flow rate in the head, neck or other areas of thebody; medication levels within the patient; patient input, e.g., when apatient has the urge to eat, the patient can push a button on a remotecontrol or other external unit to initiate the stimulation; temperatureof tissue in the stimulation target region; physical activity level,e.g. based on accelerometer recordings; brain hyperexcitability, e.g.increased response of given tissue to the same input; indicators ofcollateral tissue stimulation; and/or detection of muscle tone(mechanical strain, pressure sensor, EMG). In some embodiments, thestimulator (140) may be configured to change the stimulation parametersin a closed loop manner in response to these measurements. The sensor(203; FIG. 2) within the stimulator (140; FIG. 2) may be configured toperform the measurements. Alternatively, other sensing devices may beconfigured to perform the measurements and transmit the measured valuesto the stimulator (140).

Thus, one or more external devices may be provided to interact with thestimulator (140), and may be used to accomplish at least one or more ofthe following functions:

Function 1: If necessary, transmit electrical power to the stimulator(140) in order to power the stimulator (140) and/or recharge the powersource (145).

Function 2: Transmit data to the stimulator (140) in order to change thestimulation parameters used by the stimulator (140).

Function 3: Receive data indicating the state of the stimulator (140)(e.g., battery level, drug level, stimulation parameters, etc.).

Additional functions may include adjusting the stimulation parametersbased on information sensed by the stimulator (140) or by other sensingdevices.

By way of example, an exemplary method of treating a patient withobesity may be carried out according to the following sequence ofprocedures. The steps listed below may be modified, reordered, and/oradded to as best serves a particular application.

1. A stimulator (140) is implanted so that its electrodes (142) and/orinfusion outlet (149) are coupled to or located near the stomach.

2. The stimulator (140) is programmed to apply at least one stimulus tothe stomach. The stimulus may include electrical stimulation, drugstimulation, chemical stimulation, thermal stimulation, electromagneticstimulation, mechanical stimulation, and/or any other suitablestimulation.

3. When the patient desires to invoke stimulation, the patient sends acommand to the stimulator (140) (e.g., via a remote control) such thatthe stimulator (140) delivers the prescribed stimulation. The stimulator(140) may be alternatively or additionally configured to automaticallyapply the stimulation in response to sensed indicators of stomachactivity, digestion, or any other manifestation of obesity.

4. To cease stimulation, the patient may turn off the stimulator (140)(e.g., via a remote control).

5. Periodically, the power source (145) of the stimulator (140) isrecharged, if necessary, in accordance with Function 1 described above.As will be described below, this recharging function can be made muchmore efficient using the principles disclosed herein.

In other examples, the treatment administered by the stimulator (140),i.e., drug therapy and/or electrical stimulation, may be automatic andnot controlled or invoked by the patient.

For the treatment of different patients, it may be desirable to modifyor adjust the algorithmic functions performed by the implanted and/orexternal components, as well as the surgical approaches. For example, insome situations, it may be desirable to employ more than one stimulator(140), each of which could be separately controlled by means of adigital address. Multiple channels and/or multiple patterns ofstimulation may thereby be used to deal with various symptoms of obesityor various combinations of medical conditions.

As shown in the example of FIG. 4, a first stimulator (140) implantedwithin the patient (208) provides a stimulus to a first location; asecond stimulator (140′) provides a stimulus to a second location; and athird stimulator (140″) provides a stimulus to a third location. Asmentioned earlier, the implanted devices may operate independently ormay operate in a coordinated manner with other implanted devices orother devices external to the patient's body. That is, an externalcontroller (250) may be configured to control the operation of each ofthe implanted devices (140, 140′, and 140″). In some embodiments, animplanted device, e.g. stimulator (140), may control or operate underthe control of another implanted device(s), e.g. stimulator (140′)and/or stimulator (140″). Control lines (262-267) have been drawn inFIG. 4 to illustrate that the external controller (250) may communicateor provide power to any of the implanted devices (140, 140′, and 140″)and that each of the various implanted devices (140, 140′, and 140″) maycommunicate with and, in some instances, control any of the otherimplanted devices.

As a further example of multiple stimulators (140) operating in acoordinated manner, the first and second stimulators (140, 140′) of FIG.4 may be configured to sense various indicators of stomach activity,digestion, or any other factor related to obesity and transmit themeasured information to the third stimulator (140″). The thirdstimulator (140″) may then use the measured information to adjust itsstimulation parameters and apply stimulation to the stomach accordingly.The various implanted stimulators may, in any combination, senseindicators of stomach activity, digestion, or other factors related toobesity, communicate or receive data on such indicators, and adjuststimulation parameters accordingly.

Alternatively, the external device (250) or other external devicescommunicating with the external device (250) may be configured to sensevarious indicators of a patient's condition. The sensed indicators canthen be collected by the external device (250) for relay to one or moreof the implanted stimulators or may be transmitted directly to one ormore of the implanted stimulators by any of an array of external sensingdevices. In either case, the stimulator, upon receiving the sensedindicator(s), may adjust stimulation parameters accordingly. In otherexamples, the external controller (250) may determine whether any changeto stimulation parameters is needed based on the sensed indicators. Theexternal device (250) may then signal a command to one or more of thestimulators to adjust stimulation parameters accordingly.

The stimulator (140) of FIG. 2 may be implanted within the patient usingany suitable surgical procedure such as, but not limited to, injection,small incision, open placement, laparoscopy, or endoscopy. FIG. 5illustrates an exemplary implanted stimulator (140) that is coupled tothe stomach (10) to provide stimulation to the stomach (10). Thestimulator is coupled to the lesser curvature (25) of the stomach (10)in FIG. 5 for illustrative purposes only. It will be recognized that thestimulator (140) may be coupled to any portion of the stomach (10) asbest serves a particular application. For example, the stimulator (140)may be coupled to the greater curvature (26), cardia (20; FIG. 1A),fundus (21; FIG. 1A), antrum (23; FIG. 1A), pylorus (24; FIG. 1A), orany portion of the body (22; FIG. 1A) of the stomach (10). Additionallyor alternatively, the stimulator (140) may be coupled to any of the fivelayers of the stomach (10), to a nerve that innervates the stomach (10),or to a blood vessel that supplies the stomach (10).

The stimulator (140) may be secured to the stomach (10) or to any otherlocation within the body using any of a number of techniques. In someexamples, the stimulator (140) is sutured to the stomach (10) using oneor more sutures. Alternatively, a medical adhesive, hook, barb, or othersecuring device or material may be used to secure the stimulator (140)at a desired location.

Alternatively, an affixation member, such as an insulative backing, maybe used to couple the stimulator (140) directly to the wall of thestomach (10) or to any other structure in the body. FIG. 6A is aperspective view of an exemplary insulative backing (130) that may beused to couple the stimulator (140; FIG. 2) directly to the stomach. Asshown in the example of FIG. 6A, the insulative backing (130) may beshaped like a flat, oval pad that includes a first surface (131) and asecond surface (132) opposite the first surface (131). The first surface(131) is configured to be coupled to the stomach and the second surface(132) is configured to be coupled to the stimulator (140; FIG. 2).

The insulative backing (130) may be made out of any insulative materialknown in the art. For example, the insulative material may include, butis not limited to, silicone, ceramic, glass, or polyurethane. In someexamples, the insulative backing (130) may be flexible so as to conformto the shape of the surface to which it is applied, for example, acurvature of the stomach.

As shown in FIG. 6A, the insulative backing (130) has a length (135), awidth (136), and a thickness (134). It will be recognized that thelength (135), width (136), and thickness (134) of the backing (130) maybe any size as best serves a particular application. For example, insome embodiments, the length (135) is slightly longer than the length ofthe stimulator (140; FIG. 2) and the width (136) is approximately onehalf of an inch wide.

Furthermore, the insulative backing (130) may have any suitable shape asbest serves a particular implantation site and/or particular type ofstimulator. For example, the insulative backing (130) may have anoval-like shape, as shown in FIG. 6A. Alternatively, the insulativebacking (130) may have a rectangular shape or any other suitable shape.

FIG. 6A shows that the insulative backing (130) may include a number ofsuture holes (133) so that the backing (130) may be sutured to thestomach. Four suture holes (133) are shown in FIG. 6A for illustrativepurposes only. It will be recognized that the backing (130) may includeany number of suture holes (133) arranged in any configuration as bestserves a particular application.

Any other suitable securing device may be used to secure the backing(130) to the stomach. For example, as shown in FIG. 6B, a number ofhooks or barbs may additionally or alternatively be included on thefirst surface (131) to secure the backing (130) to the stomach. Amedical adhesive may also be used to secure the backing (130) to thestomach.

Thus, a variety of devices may be used to couple the first surface (131)of the backing (130) to the stomach. As indicated above, the stimulator(140; FIG. 2) is attached to the second surface (132) of the backing(130). The stimulator (140; FIG. 2) is then able to apply a stimulus tothe stomach via the electrode contacts (142) disposed in the backing(130). Returning to FIG. 6A, a number of electrode contacts (142) aredisposed on the first surface (131) of the insulative backing (130)through which an electrical stimulation current is applied to thestomach by the stimulator (140) coupled to the backing (130). In someexamples, the insulative backing (130) includes two electrode contacts(142), as shown in FIG. 6A. However, any number of electrode contacts(142) may be disposed on the insulative backing (130) as best serves aparticular application.

The electrode contacts (142) are oriented on one side of the insulativebacking (130) so as to direct the stimulating current to the stomach.Hence, the insulative backing (130) and the electrode contacts (142) actas current field shaping instruments. In other words, the insulativebacking (130) and/or the electrode contacts (142) disposed on thebacking (130) force current to be directed towards the stomach andreduce useless and extraneous backwards current flow around portions ofthe stimulator (140). In some embodiments, the use of the insulativebacking (130) may save up to forty percent or more of the totalstimulation energy produced by the stimulator (140). Such energyefficiency increases battery life within the stimulator (140) and allowsthe stimulator (140) to have a smaller and more convenient size.Additionally, the added energy efficiency can reduce the amount of timethe implant patient has to spend recharging the stimulator (140).Recharging the stimulator (140) may require that the patient limitmobility while energy is transferred to the stimulator (140) from anexternal charging device. The time during which recharging occurs andmobility is limited may consequently have a significant impact on thepatient. Therefore, being able to limit the time spent recharging thestimulator (140) is of great potential value.

FIG. 6C is a top view of the insulative backing (130) shown in FIG. 6A.FIG. 6C shows the first surface (131) of the insulative backing (130)and shows the two electrode contacts (142) and four suture holes (133).The spacing between the electrode contacts (142) may vary as best servesa particular application.

As mentioned, any number of electrode contacts (142) may be disposed onthe insulative backing (130). As will be explained in connection withFIGS. 7A-7H, the electrode contacts (152) may be arranged in an arraywith a variety of configurations to facilitate different types ofstimulation or provide different current steering effects. Currentsteering is also known as neuronavigation or e-trolling. As used hereinand in the appended claims, the term “current steering” will be used todescribe a process used to determine the optimal stimulation parametersfor a particular patient.

FIGS. 7A-7H illustrate a number of exemplary electrode contactarrangements that may be disposed on the first surface (131) of theinsulative backing (130). As mentioned, the stimulator (140; FIG. 2) maybe configured to provide monopolar and/or multipolar electricalstimulation. To this end, each electrode contact (142) may beselectively programmed or configured to act as an anode or as a cathode.Each electrode contact (142) may also be programmed to be “off,” i.e.,not part of the circuit delivering the stimulation current. Monopolarstimulation is achieved by using two electrode contacts of oppositepolarity that are relatively far apart from each other. Bipolarstimulation is achieved by using two electrode contacts of oppositepolarity that are relatively close to each other. Tripolar stimulationis achieved by using a cathode surrounded by two anodes or an anodesurrounded by two cathodes.

Monopolar and multipolar electrode configurations often have differentstimulation localization properties. For example, a monopolar electrodeconfiguration emits a multidirectional electrical field that may be usedto stimulate a relatively general stimulation site. A multipolarelectrode configuration, on the other hand, emits a more localizedelectrical field that is often used to stimulate a relatively specificstimulation site, and may be used to stimulate stimulation sites thathave a particular orientation (e.g., a nerve).

The electrode contacts (142) may be made of any conducting material thatwill withstand and operate effectively in an implanted environment. Suchmaterials include, for example, a conducting ceramic, conductingpolymer, copper, and/or a noble or refractory metal, such as gold,silver, platinum, iridium, tantalum, titanium, titanium nitride,niobium, and/or an alloy thereof. The use of one or more of thesematerials in constructing the electrode contacts (142) may serve tominimize corrosion, electrolysis, and/or damage to surrounding tissues.

The surfaces of the electrode contacts (142) may have any of a number ofproperties. For example, the surfaces may be smooth or rough. A roughsurface increases the actual surface area of an electrode contact andmay, with some materials (e.g., platinum or iridium), increase thepseudo-capacitance of the electrode contact. An increasedpseudo-capacitance may serve to minimize the risk of adverse electricalaffects to a patient being treated. A rough surface may also serve tohelp secure the adhesive backing (130) to the stomach.

Moreover, the electrode contacts (142) may have any size or shape thatsuits a particular application. Differently shaped electrode contacts(142) provide different current densities. For example, a round or ovalelectrode contact, as shown in FIGS. 7A-7H, may provide a more uniformcurrent density than an electrode contact that is rectangular. However,the shape of the electrode contacts (142) may vary as best serves aparticular application.

As mentioned, the electrode contacts (142) may be arranged in a varietyof array configurations to facilitate different types of stimulation.FIGS. 7A-7H illustrate a number of exemplary electrode contactarrangements that may be used to provide monopolar and/or multipolarstimulation at the stomach. However, it will be recognized that theelectrode contact arrangements shown in FIGS. 7A-7H are merelyillustrative of the many different electrode contact arrangements thatmay be used to provide monopolar and/or multipolar stimulation at thestomach.

For example, FIG. 7A shows a first electrode contact arrangement thatmay be used to provide monopolar and/or multipolar stimulation at thestomach. The electrode contact arrangement of FIG. 7A includes a centerelectrode contact (142-1) surrounded by three electrode contacts(142-2,3,4) in an equilateral triangle or trigonal planar configuration.As mentioned, each of the electrode contacts (142) may be selectivelyconfigured to act as an anode or cathode. Hence, monopolar stimulationmay be achieved by using, for example, the top electrode contact (142-2)and one of the bottom electrode contacts (e.g., 142-3) as ananode-cathode pair. Bipolar stimulation may be achieved by using, forexample, the center electrode contact (142-1) with one of the otherelectrode contacts (e.g., 142-2) as an anode-cathode pair. Tripolarstimulation may be achieved by using, for example, the center electrodecontacts (142-1) with two of the other electrode contacts (e.g., 142-3and 142-4) in an anode-cathode-anode or cathode-anode-cathodeconfiguration.

As illustrated in FIGS. 7A-7H, there are many possible configurationsfor the electrode contact array. The illustrated examples are merelyexemplary and other configurations are within the scope of theprinciples described herein. FIG. 7B illustrates a configuration with acentral electrode contact (142) and four additional electrode contacts(142) arranged in a square around the central electrode contact (142).FIG. 7C illustrated a line of four electrode contacts (142) with a lineof two electrode contacts (142) both above and below the line of four,with the lines of two electrode contacts (142) each being centered withrespect to the larger line of four. FIG. 7D illustrates a similarconfiguration only with two lines of four electrode contacts (142)arranged between the upper and lower lines of two.

FIG. 7E illustrates a configuration in which the electrode contacts(142) are arranged in a two-by-four rectangular array. FIG. 7Fillustrates a configuration in which a line of four electrode contacts(142) is disposed adjacent a line of three electrodes. FIG. 7Gillustrated a configuration with six electrode contacts (142) in threecolumns of two electrode contacts (142) each. The center column isoffset vertically with respect to the two side columns. FIG. 7Hillustrates a configuration in which the electrode contacts (142) arearranged in a circle or ring pattern. Each configuration illustrated andother possible configurations for the electrode contacts (142) willprovide different current steering options and may be particularly wellsuited for treating obesity in a particular patient.

FIG. 8 is a cross-sectional side view of an insulative backing (130) andstimulator (140) coupled to the stomach (10). As shown in FIG. 8, thefirst surface (131) of the insulative backing (130) is coupled to thestomach (10) and the second surface (132) of the insulative backing(130) is coupled to the stimulator (140). Alternatively, the stimulator(140) may be integrated with the insulative backing (130) so as to be atleast partially enclosed in the insulative backing (130). One side ofthe insulative backing (130) would still provide a first surface (131)having two or more electrode contacts (142) disposed thereon.

As shown in FIG. 8, the electrode contacts (142) are electrically and/ormagnetically coupled to the implanted stimulator (140). For example, oneor more conductive vias (210) may be used to electrically couple theelectrode contacts (142) to the electrical circuitry (144; FIG. 2) ofthe implanted stimulator (140). The conductive vias (210) may includeconductive wires, metal traces, or any other material configured toelectrically couple the electrode contacts (142) to the stimulator(140). Thus coupled, electrical stimulation generated by the stimulator(140) may be applied to the stomach (10) via the electrode contacts(142).

Returning to FIG. 5, the stimulator (140) is configured to applystimulation to the stomach (10) based on the measurements of the sensor(203; FIG. 2). In some examples, the sensor (203; FIG. 2) is configuredto sense stomach distension that occurs as food enters the stomach (10).The sensor (203; FIG. 2) may additionally or alternatively be configuredto sense electrical activity (e.g., gastric slow waves) of the stomach(10) or any other stomach or related activity as described above.

In some examples, the stimulator (140) enables or turns on thestimulation to the stomach (10) when the sensor (203; FIG. 2) senses oneor more indicators of stomach activity, digestion, or other factorsrelated to obesity. For example, the stimulator (140) may be configuredto enable stimulation of the stomach (10) when the sensor (203; FIG. 2)senses stomach distension or electrical activity produced by the stomach(10).

The various stimulation parameters (e.g., frequency, pulse width,amplitude, electrode polarity configuration, burst pattern, duty cycle,ramp on time, and ramp off time) associated with the stimulation may becontinuously adjusted in response to the sensed obesity factors. In someexamples, the stimulation parameters are automatically adjusted by thestimulator (140) in response to the sensed obesity factors. For example,the stimulator (140) may automatically increase the frequency and/oramplitude of the stimulation if the sensor (203; FIG. 2) senses anincrease in stomach distension or electrical activity produced by thestomach (10). The stimulation causes the patient to feel a sensation offullness before the stomach (10) fully distends such that the patienteats less.

The stimulator (140) may additionally or alternatively be configured tostimulate the stomach (10) during periods of time during which thepatient is not eating so that the patient feels a sensation of fullness,thereby reducing the patient's desire to eat. The frequency ofstimulation may be programmed and adjusted as best serves a particularpatient.

In some examples, the stimulator (140) is configured to provideintermittent stimulation to the stomach (10). Intermittent stimulationis also referred to as demand pacing stimulation. In intermittentstimulation, the stimulator (140) is configured to intermittentlydisable or turn off the stimulation to the stomach (10). Intermittentstimulation increases the effectiveness of the stimulation for someobese patients by preventing the stomach (10) and/or neurological systemof the patient from adapting to the stimulation. Intermittentstimulation is also beneficial in many applications because it requiresless battery power than does continuous stimulation. Hence, thestimulator (140) may operate longer without being recharged, the powersource (145; FIG. 2) may be smaller, and the overall size of thestimulator (140) may be reduced.

FIG. 9 illustrates an exemplary configuration wherein multiplestimulators (140-1, 140-2) are coupled to the stomach (10) to providestimulation to the stomach (10). FIG. 9 shows a first stimulator (140-1)coupled to the lesser curvature (25) of the stomach (10) and a secondstimulator (140-1) coupled to the greater curvature (26) of the stomach(10). However, it will be recognized that any number of stimulators(140) may be coupled to any portion of the stomach (10) as best serves aparticular application.

In some examples, stomach distension may be sensed by measuring thedistance between two stimulators (140) that are coupled to the stomach(10). For example, the separation distance (141) between the stimulators(140-1, 140-2) of FIG. 9 may be measured to sense stomach distension. Asthe stomach (10) distends due to the intake of food, the separationdistance (141) increases. One or more of the stimulators (140-1, 140-2)may then turn on, adjust, or turn off stimulation to the stomach (10) inresponse to this change in separation distance (141) between thestimulators (140-1, 140-2).

In some embodiments, the stimulators (140-1, 140-2) are configured tosense the separation distance (141) by communicating with each otherusing one or more RF fields. For example, the first stimulator (140-1)may be configured to transmit an RF field and the second stimulator(140-2) may be configured to sense the signal strength of the RF fieldtransmitted by the first stimulator (140-1). When the stomach (10)distends due to an intake of food, the separation distance (141) betweenthe two stimulators (140-1, 140-2) increases, thereby decreasing thesensed signal strength of the transmitted RF field. The secondstimulator (140-2) senses this decrease in signal strength of the RFfield transmitted by the first stimulator (140-1). One or more of thestimulators (140-1, 140-2) may then stimulate the stomach (10) inresponse to this decrease in sensed signal strength of the transmittedRF field. The stimulation applied may be proportional to the decrease insignal strength of the transmitted RF field allowing for a continuum ofpossible stimulation levels dictated by the amount of stomachdistention. It will be recognized that the first and second stimulators(140-1, 140-2) may communicate via any suitable communication linkincluding, but not limited to, an infrared (IR) link, an optical link,or Bluetooth™.

FIG. 10 illustrates an exemplary configuration wherein a stimulator(140) is configured to stimulate the stomach (10) via a number ofelectrodes (142) disposed on a lead (141). As shown in FIG. 10, thestimulator (140) may be implanted in any convenient location in thepatient, e.g., in the abdominal wall. The lead (141) extends away fromthe stimulator (140) towards the stomach (10) such that its electrodecontacts (141) touch or are in close proximity to the stomach (10). Insome embodiments, the lead (141) may additionally be coupled to a sensor(203) that is also located at or near the stomach (10). A catheter (143;FIG. 2) may additionally or alternatively be coupled to the stimulator(140) and configured to apply one or more drugs to the stomach.

The preceding description has been presented only to illustrate anddescribe embodiments of the invention. It is not intended to beexhaustive or to limit the invention to any precise form disclosed. Manymodifications and variations are possible in light of the aboveteaching.

1.-20. (canceled)
 21. A neurostimulation kit, comprising: a stimulationbacking including a flat, electrically insulative, body having a pair ofopposing first and second planar surfaces, and an electrode affixed tothe first surface of the insulative body, the stimulation backingconfigured for being implanted within a patient and affixed therein toplace the electrode into contact with a tissue surface of the patient;and an implantable neurostimulator including a housing and stimulationcircuitry contained within the housing, the neurostimulator configuredfor being implanted within the patient by affixing the housing to thesecond surface of the insulative body, such that the stimulationcircuitry is electrically coupled to the electrode.
 22. Theneurostimulation kit of claim 21, wherein the insulative body isflexible to conform to a curvature of the tissue surface.
 23. Theneurostimulation kit of claim 21, wherein the insulative body iscomposed of an electrically insulative material selected from the groupconsisting of silicone, ceramic, glass, and polyurethane.
 24. Theneurostimulation kit of claim 21, wherein the stimulation backingincludes a plurality of suture holes formed within the insulative body.25. The neurostimulation kit of claim 21, wherein the stimulationbacking includes hooks or barbs located on the first surface of theinsulative body.
 26. The neurostimulation kit of claim 21, wherein thestimulation backing includes a plurality of electrodes affixed to thefirst surface of the insulative body.
 27. The neurostimulation kit ofclaim 21, wherein the stimulation backing includes an electricallyconductive via coupled to the electrode, wherein the stimulationcircuitry of the neurostimulator is electrically coupled to the via whenthe housing is affixed to the second surface of the insulative body. 28.The neurostimulation kit of claim 21, wherein the neurostimulatorincludes a power source contained within the housing.
 29. Theneurostimulation kit of claim 21, wherein the housing includes aninternal space equal to or less than 3 cubic centimeters.
 30. A methodof treating a patient using a stimulation backing and anneurostimulator, the stimulation backing including a flat, electricallyinsulative, body having a pair of opposing first and second planarsurfaces, and an electrode affixed to the first surface of theinsulative body, and the neurostimulator including a housing andstimulation circuitry contained within the housing, the methodcomprising: affixing the insulative body within the patient, therebyplacing the electrode into contact with a tissue surface of the patient;affixing the housing to the second surface of the insulative body, suchthat the stimulation circuitry is electrically coupled to the electrode;and operating the neurostimulator to convey stimulation energy from thestimulation circuitry to the tissue surface via the electrode to treatthe patient.
 31. The method of claim 30, further comprising conformingthe insulative body to a curvature of the tissue surface.
 32. The methodof claim 30, wherein the insulative body is composed of an electricallyinsulative material selected from the group consisting of silicone,ceramic, glass, and polyurethane.
 33. The method of claim 30, whereinthe insulative body is sutured to the tissue surface.
 34. The method ofclaim 30, wherein the insulative body is affixed to the tissue surfacevia hooks or barbs.
 35. The method of claim 30, wherein the stimulationbacking includes an electrically conductive via coupled to theelectrode, wherein the stimulation circuitry of the neurostimulator iselectrically coupled to the via when the housing is affixed to thesecond surface of the insulative body.
 36. The method of claim 30,wherein the neurostimulator includes a power source contained within thehousing.
 37. The method of claim 30, wherein the housing includes aninternal space equal to or less than 3 cubic centimeters.
 38. The methodof claim 30, wherein the housing is affixed to the second surface of theinsulative body after the insulative body has been affixed within thepatient.
 39. The method of claim 30, wherein the insulative body isaffixed to a stomach of the patient, thereby placing the electrode intocontact with an external surface of the patient.
 40. The method of claim39, wherein the patient suffers from obesity, and stimulation energyconveyed from the stimulation circuitry to the external surface of thestomach treats the obesity.